1. Field:
The invention is concerned in general with the use of controlled flow of air or other gas in opposition to normal gas flow in a conduit as a control for such normal gas flow.
2. State of the Art:
Mechanical valves or dampers are normally employed to control flow of fluids through conduits. Heretofore, controlling flow of a fluid through a Venturi has been proposed by injecting a control fluid through openings circumferentially of the Venturi section of a flow conduit, but this provides only a minimum range of control without the possibility of complete shut-off. Nozzles positioned coaxially of respective flowing streams of a liquid or a gas have also been proposed for controlling flows of such streams, but these are impractical for many uses.